For certain construction projects, rigid members, such as piles, anchor members, caissons, sheet pile barriers, and mandrels for inserting wick drain material, must be placed into the earth. The term “piles” will be used herein to refer to the rigid members typically driven into the earth during construction projects. It is well-known that such rigid members may often be driven into or extracted from the earth without excavation by applying a driving or extracting force on an upper end of the pile.
To drive or extract a pile, a driving force is typically applied to the pile along a longitudinal axis A of the pile. The driving force may be created in various ways. A drop hammer comprises a ram member that is repeatedly raised and dropped such that the impact of the ram member drives the pile into the earth. A diesel hammer comprises a ram member that compresses and ignites fuel between the ram member and the pile; the impact of the ram member drives the pile, while expansion of the ignited fuel both drives the pile into the earth and raises the drop hammer for the next impact. A hydraulic drive system uses a hydraulic ram to force or crowd the pile into the earth. A crane may be used to apply an extraction force on a pile through a cable.
In addition, vibratory forces may be applied to the pile. Vibratory forces are also applied along the longitudinal axis A of the pile, typically in combination with a passive driving force created by the weight of the vibration equipment on top of the pile. The combination of the passive driving force and the vibratory forces is often sufficient to drive a pile in certain soil types. Typically, a suppressor is used to isolate support equipment such as a crane or the like from the vibratory forces.
Attempts have been made to combine vibratory forces with active driving forces such as a hydraulic drive system. U.S. Pat. Nos. 6,039,508 and 6,431,795 to White disclose systems and methods for inserting wick drain material comprising a bottom drive system that combines a vibratory device with a gear drive to drive a mandrel supporting the wick drain mater. The gear drive crowds the mandrel into the earth, and the vibratory device is operated to assist the gear drive under some soil conditions.
The need exists for improved vibratory pile driving systems and methods.